1. Field
Various features relate to stacked redistribution layers on a die
2. Background
A die can be defective for many reasons. The process of manufacturing dies can cause cracking in dies, which can result in defective dies. In addition, dies can be defective or fail when they are subject to relative high operating current, which can cause fast electromigration (EM) degradation near the redistribution layer/ball region in a die.
FIG. 1 illustrates a side view of a die. Specifically, FIG. 1 illustrates a side view of a die 100 that includes a substrate 101, several metal and dielectric layers 102, a pad 104, a passivation layer 106, a first insulation layer 108, a metal redistribution layer (RDL) 110, and a second insulation layer 114. FIG. 1 also illustrates a solder ball 116 on the die 100. Specifically, the solder ball 116 is coupled to the metal redistribution layer 110. The pad 104 and the metal redistribution layer 110 are a conductive material. For example, the pad 104 may be an aluminum material and the metal redistribution layer 110 may be a copper material. The first insulation layer 108 and the second insulation layer 112 are polyimide layers.
Fast EM degradation may occur at a RDL/ball region of a die due to high current and rapid copper-tin (CuSn) intermetallic formation. An example of a RDL/ball region on a die is represented by region 118 of the die 100 in FIG. 1. The result of the CuSn intermetallic formation is an EM inducted void at the RDL/ball region 118 of the die 100. Specifically, the copper material of the metal distribution layer 110 may diffuse towards the solder ball 116, creating a void at the interface (e.g., region 118) of the metal distribution layer 110 and the solder ball 116. The void that is created between the metal distribution layer 110 and the solder ball 116 prevents a current from traversing to/from the solder ball 116 to the circuits (e.g., circuit elements in the substrate 101) of the die 101. In a die that operates at high current, the rate of diffusion is substantially greater, thus reducing the lifespan of the die and/or causing the die to be defective.
Therefore, there is a need for die that is more resistant to fast electromigration (EM) degradation.